For starting an internal combustion engine, which has am electro-hydraulic valve gear, a pressure supply system for the valve gear is required to form the pressure. The faster the pressure build-up in the supply system for the electro-hydraulic valve gear can take place, the shorter the start time of an internal combustion engine, which aids in the careful treatment of the Kfz-battery in low temperature and limits wear on the battery during the cold start phase.
Increasingly, motor vehicles with a variable or fully variable valve control (VVC) are being developed. The goal of these inventions is an increase of the engine efficiency, for example, by means of the throttle and optimizing the gas-changing to the cylinders of the internal combustion engine. One direction of development is provided in the electro-hydraulic valve control (EHVC). With the electro-hydraulic valve control, the force introduction in the gas-change valve takes place in a hydraulic manner, the control of the force flow being electric, for example, through the use of magnetic valves. For production of the operating pressure in the supply system of the electro-hydraulic valve gear, a supply pressure is produced on its primary pump, which is made ready by means of the lubricating oil pump of the internal combustion engine.
In low temperatures, which can cause a reduced durability of the vehicle battery, the starter that starts the internal combustion engine must turn-over the battery longer, in order to produce the required supply pressure to the primary pump of the electro-hydraulic valve gear alone with the lubricating oil pump of the internal combustion engine. During the starting-phase of an internal combustion engine, all of the bearings of the internal combustion engine are no provided with a friction-reducing amount of lubricating oil, so that during the starting-phase, high wear in the contact areas of the components moveable relative to one another can occur. Therefore, a shortening of the starting-phase of an internal combustion engine is necessary.
The primary advantage of the solution of the present invention lies in a drastic shortening of the starting-time of an internal combustion engine, whether it is a compression internal combustion engine or an internal combustion engine with vacuum pipe injection or direct fuel injection. With the present invention, the time span in which the internal combustion engine is exposed to the highest wear is drastically reduced. This positively affects the starting-phase of the internal combustion engine, in particular, when the engine is started in the colder seasons with reduced voltage levels in the vehicle battery. The shorter the starting-phase of an internal combustion engine, the smaller the load is on the starter and, therewith, the load on the vehicle battery.
With the proposed solution of the present invention, a started can be completely avoided, when, with adequate dimensioning of the starting pressure pump module with an electric starting pressure pump, a direct start of the internal combustion engine with the electro-hydraulic valve control (EHVC) can be bought about without interposition of a starter. This is achievable with internal combustion engines with direct fuel injection, in that a control apparatus arranged in the direct-injection engine and a start function there, respectively, can supply each, nearest possible cylinder of the internal combustion engine with the mixture and ignite the same for starting.
When the required supply pressure for operation of the electro-hydraulic valve gear is produced by means of a supply unit with a separate drive, the pressure buildup in the electro-hydraulic valve gear system is independent from the rotation (starter movement) of the internal combustion engine. Thereby, a faster overall oiling of the engine is produced by means of supply pressure production, which, particularly, during the cold seasons and with viscous lubricating agents, is very desirable, in order to keep the wear that occurs during the starting-phase to a minimum. In particular, with low temperatures, based on the qualities of the lubricating material is must be accurately determined that the critical area, that is, the bearings of moveable components such as the connecting rod-bearing/crank-bearing, etc., are supplied with a sufficient supply of lubricating material, and the lubricating material already supplied during the starting-phase is continuously circulated. An advantageous variation of the invention solution is that diesel systems or internal combustion engines with direct fuel-injection systems with a common rail, which are provided with an electric fuel pump, also can be used for pressure production in a supply system of the electro-hydraulic valve gear. The electric fuel pump, therefore, can be engaged with several functions, so that through interposition of a pressure converter, various pressure levels for various systems on the internal combustion engine can be set and can be supplied permanently with the corresponding operating pressure.